Almost every part of the body may be studied with magnetic resonance imaging (MRI). The clear pictures obtained from an MRI often provide physicians with information not available through other diagnostic tests such as x-rays, and in some cases may even eliminate the need for exploratory surgery such as arthroscopy.

To gather information about various conditions affecting the body, including those causing unexplained chronic pain, physicians may use several types of MRI scanners, including:

• Standard MRI. This scanner resembles a long cylinder with a narrow tube in the center. A patient lies on a moveable bed and the whole body is inserted inside the tube. Although this machine may be confining for some people, it produces the clearest images.
  
  
• Short-bore MRI. This scanner is similar to the standard, except only half the size. Depending on which areas of the body are being tested, patients position their bodies so that the part being scanned lies within the tube. People who experience anxiety in enclosed spaces may prefer this scanner.
  
  
• Open MRI. This scanner, which is often shaped somewhat like the letter “C,” may be an option for obese or claustrophobic patients because there is additional room inside the machine. Some facilities offer upright open MRIs in which the patient stands. However, the images produced by open MRIs are not as detailed as those of other MRI scanners.

Researchers are constantly trying to improve MRI and other diagnostic technologies. Newer types of MRI, whose availability may be limited, include:

• 3.0-Tesla MRI. The strength of MRI is rated in units called Tesla units, with standard high-field MRI at 1.0 to 1.5 Teslas. Some facilities now have powerful 3.0-Tesla and 4.0-Tesla MRI, and 7.0-Tesla MRI is being developed for brain imaging. Research has indicated that 3.0-Tesla MRI can diagnose shoulder cartilage tears noninvasively with an accuracy comparable to that of arthroscopy.
  
  
• High-resolution prostate MRI. Scientists at Johns Hopkins University and elsewhere are working to make advanced MRI available soon to provide the first reliable screening for prostate cancer, to avoid blind biopsies and questionable blood tests, physical examinations and ultrasounds.
  
  
• Voxel-based morphometry (VBM). This permits very sensitive measures of small sections of the brain. VBM has been used in studying conditions such as depression.
  
  
• Magnetic resonance spectroscopic imaging (MRSI). Spectroscopy uses means such as prisms to split radiant energy into its wavelengths or frequencies. Spectroscopic MRI has been found useful in diagnosing cancer.
  
  
• Nuclear magnetic resonance (NMR) spectroscopy. This low-energy technique avoids deposits of heat in patients and medical staff by detecting “nuclear spin” of particles. A goal is to create a portable, lightweight variation of MRI.
  
  
• Whole-heart MRI. A potential noninvasive alternative to procedures such as cardiac catheterization in detecting coronary artery disease.
  
  
• Real-time functional magnetic resonance imaging (rtfMRI). In addition to its diagnostic uses, MRI may have a role in pain management by providing a kind of biofeedback. Researchers have used rtfMRI to provide chronic pain patients with live, visual images of pain centers in their brain. With real-time MRI, some patients have been able to ease their pain by applying mental strategies similar to guided imagery.